1. Field of the Invention
The present invention relates to an abnormality diagnosis device and an abnormality diagnosis method for a supercharger.
2. Description of Related Art
In an internal combustion engine equipped with a supercharger, an intake air amount and a supercharging pressure of the internal combustion engine are adjusted, so that an output torque thereof is controlled to be a target torque determined by an accelerator operation amount and so on. To be specific, a target intake air amount and a target supercharging pressure of the internal combustion engine can be obtained based on the target torque determined by the accelerator operation amount and so on. Moreover, the opening of a throttle valve and the rotation speed of the supercharger are adjusted in such a way that the intake air amount of the internal combustion engine is controlled to be the target intake air amount and the supercharging pressure of the internal combustion engine is controlled to be the target supercharging pressure.
Further, as shown in the Japanese Patent Application Publication No. 2008-25529 (JP 2008-25529A), an abnormality diagnosis device for determining the presence and absence of an abnormality of the supercharger is disposed in a vehicle equipped with an internal combustion engine having a supercharger. An abnormality determination processing described as follows is executed in this abnormality diagnosis device, that is, comparing an actual supercharging pressure of the internal combustion engine and a prescribed reference value, and determining the presence and absence of an abnormality of the supercharger according to the comparison result. In addition, the above-mentioned actual supercharging pressure is the pressure of a part that is closer to the upstream than the throttle valve and closer to the downstream than the supercharger in the intake passage of the internal combustion engine, and the actual supercharging pressure is detected by a supercharging pressure sensor. Further, for example, the following processing in [A] or [B] can be executed as the abnormality diagnosis processing.
[A] When the actual supercharging pressure is adjusted, an upper-limit supercharging pressure for preventing over-speed rotation of the supercharger is obtained based on the intake air amount of the internal combustion engine and so on, so that the actual supercharging pressure could not rise beyond the upper-limit supercharging pressure. The upper-limit supercharging pressure is set to be the above-mentioned reference value, and it is determined that there is the abnormality of the supercharger according to the fact that the actual supercharging pressure becomes equal to or above the reference value (the upper-limit supercharging pressure).
[B] When the actual supercharging pressure is adjusted, the above-mentioned target supercharging pressure, as an index of the adjustment, is obtained. The target supercharging pressure is set to be the above-mentioned reference value, and it is determined that there is the abnormality of the supercharger according to the fact that the deviation of the actual supercharging pressure with respect to the reference value (the target supercharging pressure) becomes equal to or above a determination value.
However, when the target output torque decreases as the accelerator operation amount operated by the driver is reduced, the target intake air amount will be reduced and the target supercharging pressure will be decreased, so that the output torque of the internal combustion engine is adjusted to be the target output torque. Moreover, the opening of the throttle valve is reduced and the rotation speed of the supercharger is decreased, so that the intake air amount and the actual supercharging pressure of the internal combustion engine are adjusted to be the target intake air amount and the target supercharging pressure respectively.